"When the government unions and the government employees are in subjective jobs, no matter how decent the people are—let's assume they are all perfect—their biases have to come through," he contended on "Squawk Box."

In 2012, public-sector workers had a union membership rate of 35.9 percent—more than five times higher than the private sector's 6.6 percent participation rate, according to the BLS.

"The IRS: They want bigger government, better wages. The BLS wants more government and better wages," he continued. "Now you're asking them to make subjective [decisions]. You don't ask firemen to do that."

In the case of the BLS, Welch said he's not claiming the government's monthly employment report is being manipulated, just that he believes human nature makes it impossible for the data-collection workers to check their personal views at the door.

Fueling his skepticism, Welch cited the September employment report, which was announced in October 2012—one month before the presidential election.

At the time, he ignited a firestorm with a Tweet that questioned the growth of nonfarm jobs by 873,000—the largest one-month increase since Ronald Reagan's presidency in 1983—and the unemployment rate drop to 7.8 percent.

Reflecting on those numbers Tuesday, Welch said they had indicated strong fourth-quarter economic growth that never materialized. In fact, he added, GDP in the final three months of 2012 was the "lowest number in the whole recovery."